Fuel oil for compression ignition engines



Patented Mar. 8, 1932 UNITED STATES PATENT OFFICE WILLIAM HELMORE, OF FARNBOROUGH, ENGLAND, ASSIGNOR '10 IMPERIAL CHEMICAL INDUSTRIES LIMITED, A CORPORATION OF GREAT, BRITAIN FIIEL OIL FOR COMPRESSION IGNITION ENGINES N0 Drawing. Application filed March 11, 1931, Serial No. 521,877, and in Great Britain February 13, 1930.

This invention relates to improvements connected with fuel oil and primers for compression ignition engines of the Diesel type:

and particularly for high-speed compression ignition engines wherein an unduly long delay period tends to occur between the injection of the fuel oil and its ignition.

It has been proposed in British patent specification No. 294,129 to shorten said de'- lay period in compression engines by adding to the fuel oil a primer which explodes at a temperature below the ignitiontemperature of the fuel oil, bursts the drops of fuel oil and causes ignition of the fuel oil.

The present invention consists according to one of its features in adding to high-boiling or nonvolatile fuel oil for a compression ignition engine, e. g. shale oil, at least two primers, at least one of which has a lower spontaneous ignitiontemperature than the fuel oil and a second ofwhich has a higher spon taneous ignition temperature than the first, whereby ignition of the primers takes place serially or in succession, ignition and combustion of one primer starting ignition or explosion of another primer. Preferably the said primers should be soluble in the fuel oil or capable of forming a. stable suspension therein.

It is believed that the operation of the mixed primers takes place in two successive stages. namely, a. first stage wherein the primer of lowest spontaneous ignition temperature (which I term the igniting primer) is ignited at a relatively low compression temperature, thereby initiating combustion of the fuel oil, and a second stage wherein the second primer or primers (which I term the exploding primer) is ignited or exploded by' the combustion of the first primer. thereby assisting ignition and/or accelerating coinbustion of the fuel oil by disruption of the drops of fuel oil. However, these stages may follow one another in such rapid sequence as to appear unseparated.

When using two primers according to the invention :-Preferably the igniting primer consists of methyl or ethyl nitrate, which has the property of rapid spontaneous ignition at a low temperature. Preferably, the exploderally as Diesel engine fuel.

ing primer consists of any of the following substances :ethyl nitrate, peroxide derivatives of organic substances such as, in the aromatic series, benzoyl peroxide; in the aliphatic series, peroxides of ole-fine hydrocarbons, e. g. amylene peroxide: polynitro (lerivatives such as picric acid (trinitrophenol) dinitrobenzene: also trinitroglycerine, hexannotliylcnetriperoxidediamine, trinitrotoluenc.

In general, both methyl nitrate and ethyl nitrate are spontaneously ignited in air at temperatures considerably lower than those at which the above named exploding primers spontaneously ignite or explode when heated in the presence of air. Methyl nitrate has a lower spontaneous ignition temperature than has ethyl nitrate and consequently ethyl nitrate may be used eitherias igniting primer with one or more of the other named substances as exploding primers or it may be used as exploding primer with methyl nitrate asv igniting primer. The successive ignitions of the two (or more) primers in the drops of oil as injected into the compressed air in the engine cylinder have a cumulative effect in accelerating ignition and combustion of the non-volatile or high boiling oil used gen- The cumulative action of two or more different compounds spontaneously ignited at increasing temperatures with ignition and combustion of each compound successively accelerating the ignition and combustion of the others, is highly advantageous in reducing the compression required in the engine cylinder in order to effect ignition of theoil.

The quantity of the primers required for the purpose of causing rapid ignition and combustion of the fuel oil in compression ignition engines is small, say for example, 1.4

to 7 per cent of ethyl nitrate and up to 2 per cent of the exploding primer by weight of fuel oil.

When using the primers, the explodingprimer may be mixed in solution in the igniting primer before addition of the mixture to the fuel oil, whereby the exploding primer and/or the igniting primer is rendered soluble in the oil and safer to handle. For

example, 1.0 per cent'trinitrotoluene may be dissolved in 6.3 per cent ethyl nitrate and The primers, or' any of them, before addition to the fuel oil may be first dissolved in a suitable solvent (which may be fuel oil itself) to form a solution miscible with the fuel oil.

The employment of igniting and exploding primers possesses the advantage that it makes possible the use of primers, which, having high spontaneous ignition temperatures when in solution in fuel oil, could not be readily exploded alone, i. e. without the assistance of an igniting primer. The heating of the exploding primer is more rapid when using the igniting primer than when the eX- ploding primer is heated only by the air under compression.

The use of methyl or ethyl nitrate or other suitable igniting primer with the exploding primer is more eflicient in comparison with previous methods of adding a single substance of low spontaneous ignition temperature (such as a nitrous or nitric ester, e. g; methyl nitrate or amyl nitrate) to fuel oil.

The invention by using the igniting primer results in an increased power output from a given engine or enables the employmentof lower compression pressures and temperatures than those that have hitherto been used, and by using the exploding primer at the same time results in acceleration of the combustion of the fuel oil whereby higher rotational speeds for compression ignition engines may be obtained than hitherto.

It should be emphasised that the primers herein described are not suitable for use in volatile fuels for engines which are sparkfired; in fact certain of the said primers have a pronounced deleterious effect upon such fuels, in that they promote combustion knock in such engines.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specfic embodiments thereofIeXcept as defined in the appended claims.

claim:

1. In methods of making improved liquid adapted to be ignited in succession, whereby the combustion of one of said compounds accelerates ignition and combustion of another of said compounds, thereby effecting a cumulative acceleration 'of fuel oil ignition in the engine.

2. In accelerating ignition and combustion of high boiling fuel oil in internal combustion engines of the Diesel type efi'ectin'g ignition of injected fuel solely by compression of air in the engine cylinder, a method which comprises incorporating with the high boiling fuel oil in small proportions ethyl nitrate and at least oneother compound having the property of spontaneously igniting in air at a temperature different from the spontaneous ignition temperature of ethyl nitrate.

3. A new and improved fuel for internal combustion engines effecting ignition of injected fuel solely by compression of air in the engine cylinder which comprises a high boiling fuel oil and incorporated therein small proportions of methyl nitrate and of ethyl nitrate.

4. A new and improved fuel for-internal combustion engines efiecting ignition of injected fuelsolely by compression of air in the engine cylinder which comprises a high boiling fuel oil and incorporated therein from 1.4 to 7 per cent of ethyl nitrate and from 1 to 2 per cent of trinitrotoluene.

5. A new and improved fuel for internal combustion engines effecting ignition of injected fuel solely by compression of air in the engine cylinder which comprises a high boiling fuel oil and incorporated therein a small proportion of ethyl nitrate and a yet smaller proportion of a polynitrated explosive such as trinitrotoluene.

In testimony whereof, I aflix my signature.

VILLIAM HELMORE. 

